This present invention relates generally to manufacturing objects. More particularly, the invention relates to a method and structure for manufacturing bonded substrates using multiple photolithography tools. Merely by way of example, the invention has been applied to the processing of a number of substrates using different photolithographic steppers characterized by different tolerance criteria for alignment and the subsequent joining of the substrates to form a composite substrate structure. The method and structure can be applied to semiconductor devices as well as other composite structures, for example, glass substrates for display applications and sensors.
The manufacturing of a variety of micro-electromechanical systems (MEMS) and micro-electromechanical devices utilizes wafer bonding. In some MEMS, including accelerometers and micro-mirrors, a sealed microcavity is used to protect the device from exposure to outside environments, while allowing the MEMS to perform the desired mechanical functions. In other MEMS application, a vacuum-sealed package is formed by wafer bonding of substrates, followed by subsequent packaging processes.
Wafer bonding techniques commonly employ a process for joining two substrates. In some cases, the substrates that are joined together are made of dissimilar materials or have been processed using different processing techniques. In particular, for some MEMS applications, silicon substrates fabricated using a first processing sequence performed using a first photolithography tool or stepper are bonded to glass substrates fabricated using a second processing sequence performed on a second photolithography tool. When different photolithographic steppers are used in the fabrication process for different substrates, it is possible that misalignment of the substrates can result, producing device failures at locations where elements on the first substrate (in some cases a silicon substrate) are misaligned with respect to elements on the second substrate (in some cases a glass substrate).
From the above, there is a need in the art for improved methods and structures for the manufacturing of bonded substrates using multiple photolithography tools.